Isoniazid (INH) is a drug commonly used to treat TB worldwide. Sometimes, the bacteria that cause TB can become resistant to INH. Resistance means that bacteria have adapted to a drug and are able to live in the presence of the drug. When TB becomes resistant to INH, INH does not work as well at fighting the bacteria. This study will treat people with INH-resistant TB with different doses of INH to see if INH can still fight the bacteria if we just increase the dose. We will compare how well the drug works at higher doses for participants who have resistant TB to how well the drug works at regular doses for participants who have TB that is not resistant. The study will also compare the safety and tolerability of the different doses of INH. Tolerability is how well people can put up with the side effects of a drug. Using increased doses of INH to treat TB that is resistant to INH is experimental and has not been approved by regulatory authorities. While there is some evidence that this approach will work, this has not yet been proven.